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About 10,000 papers for “Differential coding”

Differential Sparse Coding

David M. Bradley, J. Andrew Bagnell · Figshare · 2018

Prior work has shown that features which appear to be biologically plausible as well as empirically useful can be found by sparse coding with a prior such as a laplacian (L1 ) that promotes sparsity. We show how smoother priors can preserve the benefits of these sparse priors while adding stability to the Maximum A-Posteriori (MAP) estimate that makes it more useful for prediction problems. Additionally, we show how to calculate the derivative of the MAP estimate efficiently with implicit differentiation. One prior that can be differentiated this way is KL-regularization. We demonstrate its effectiveness on a wide variety of applications, and find that online optimization of the parameters of the KL-regularized model can significantly improve prediction performance.

Cited by 52Open access

Functional Coding of Differential Forms

Jerzy Karczmarczuk · 1999

Algebraic computations in differential geometry have usually a strong "analytic" side, and symbolic formula crunching is heavily used, even if at the end, the user needs only numbers, or graphic visualization. We show how to implement in a simple way the domain of differential forms with the p-vector algebra, Hodge "star" operator, and the differentiation. There is no explicit symbolic manipulation involved, we exploit only the "standard" mathematical operations in a generic way. Everything forms a local algebra coded in Haskell, and the differentiation algorithms heavily use the lazy evaluation. Some short examples are presented. This paper generalizes our one-dimensional algorithmic differentiation formalism in functional sauce presented elsewhere.

Cited by 10

Coding CPFSK for differential demodulation

Griffin, Anthony · University of Canterbury Research Repository (University of Canterbury) · 2000

A differential encoder is developed that preserves the phase trellis of continuous phase frequency shift keying (CPFSK) through differential demodulation. This differential encoder interfaces well with the decomposed model of CPFSK, creating a decomposed model of differentially-encoded and differentially-demodulated CPFSK (DCPFSK). The normalised minimum squared Euclidean distance d2min of uncoded DCPFSK is calculated. A code search model is developed, allowing codes over rings to be specifically designed for DCPFSK. The results of code searches show that there is very little loss in d2min when comparing coded DCPFSK systems with coherently-demodulated coded CPFSK systems. The performance of uncoded and coded DCPFSK systems in both additive white Gaussian noise (AWGN) and Rayleigh flat fading is analysed and simulated. DCPFSK is shown to be relatively robust to medium to slowly-varying fading, without the use of any additional techniques. Rate-1/2 encoded quaternary DCPFSK with modulation index h = 1/4 is compared with coherently-demodulated uncoded MSK and differentially-encoded and differentially- demodulated minimum shift keying (DMSK) without error-control coding, in AWGN and Rayleigh flat fading. The coded system shows that significant performance improvement can be obtained through simple coding, particularly in Rayleigh flat fading.

Cited by 0Open access

A Costas loop with Differential Coding

János Ladvánszky · International Journal of Contemporary Research and Review · 2017

When a Costas loop is used for QAM demodulation, the received constellation diagram rotates. Rotation causes degradation of the symbol error rate (SER). In this paper we propose differential coding to eliminate the effects of rotation, with SER of  0.004 at SNR of 0 dB.

Cited by 3Open access

Pre-Coding Aided Differential Spatial Modulation

Meng Zhang, Miaowen Wen, Xiang Cheng et al. · 2015 IEEE Global Communications Conference (GLOBECOM) · 2014

In this paper, we propose a novel Multiple Input Multiple Output (MIMO) scheme based on Spatial Modulation (SM) and termed as Pre-coding aided Differential Spatial Modulation (PDSM). By mapping information to the receiver side space-time transmit blocks and conducting differential modulation, the PDSM scheme achieves further reduced receiver side complexity in comparison with Pre-coding aided Spatial Modulation (PSM). A general upper bound on the Average Bit Error Probability (ABEP) achieved by the PDSM architecture with an arbitrary number of transmit antennas and two receive antennas is derived, and an exact closed-form ABEP expression is provided for BPSK signaling in Rayleigh fading environment. The PSM architecture with the same system configuration is chosen as a benchmark for performance comparisons. Simulation results validate the analysis and reveal a less-than-3dB Signal-to- Noise power Ratio (SNR) penalty of the considered system in comparison with the benchmark.

Cited by 12

Differential block coding of bilevel images

George R. Robertson, Maurice F. Aburdene, Richard J. Kozick · IEEE Transactions on Image Processing · 1996

In this correspondence, a simple one-dimensional (1-D) differencing operation is applied to bilevel images prior to block coding to produce a sparse binary image that can be encoded efficiently using any of a number of well-known techniques. The difference image can be encoded more efficiently than the original bilevel image whenever the average run length of black pixels in the original image is greater than two. Compression is achieved because the correlation between adjacent pixels is reduced compared with the original image. The encoding/decoding operations are described and compression performance is presented for a set of standard bilevel images.

Cited by 14

Multiring Differential Chain Coding for line drawings

Johannessen, A.B. (author) · Research Repository (Delft University of Technology) · 1990

A new type of chain codes, named multiring differential chain code (MRDCC), is introduced. The distortion and coding rate are investigated and compared with the standard chain code (SCC), multiring chain code (MRCC) and differential chain code (DCC). The results show that MRDCC offers the highest performance among these codes. The experimental observations are in good agreement with the theoretical results.

Cited by 0

Differential coding in networked controlled linear systems

Carlos Canudas de Wit, Francisco R. Rubio, Juan Fornés et al. · SPIRE - Sciences Po Institutional REpository · 2006

This paper investigates the closed-loop properties of the differential coding scheme known as Delta–Modulation when used in feedback loops within the context of linear systems controlled through some communication network. We propose a new modified scheme of the original form of the Delta M algorithm which improves the closed-loop properties. The new coding structure explicitly uses information from the system model. Stability properties for both: the continuoustime and the discrete-time version of this new algorithm are assessed. The results shows that the stability domain and the resulting precision of the Delta M is limited by the position of the unstable poles of the system.

Cited by 0Open access

An edge preserving differential image coding scheme

Martin Rost, Khalid Sayood · 1990

Differential encoding techniques are fast and easy to implement. However, a major problem with the use of differential encoding for images is the rapid edge degradation encountered when using such systems. This makes differential encoding techniques of limited utility, especially when coding medical or scientific images, where edge preservation is of utmost importance. A simple, easy-to-implement differential image-coding system that has excellent edge preservation properties is presented. The coding system can be used over variable-rate channels, which makes it especially attractive for use in the packet network environment.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Cited by 3

Generalized differential coding theorem and its applications

B. Hirosaki · Electronics and Communications in Japan (Part I Communications) · 1984

Abstract A differential coding method regards the transmission line code as a kind of state and assigns the original codeword to each state transition. This method is used widely to regenerate the original codeword as an invariant for the state transition even if there exists state ambiguity during transmission. This paper derives a differential coding theorem as the necessary and sufficient condition for the existence of a differential code on the basis of the mathematical formulation of differential coding problems. According to the theorem, the necessary and sufficient condition for the existence of a differential code is that the set of ambiguity operators should be an irreducible and nonseparable group G σ , and that a stationary successive operator, which is antihomomorphism on G σ , should exist. the importance of the theorem is demonstrated through the differential coding for the staggered QAM transmission system, which has been considered difficult to code differentially. Since the theorem is derived under some general conditions, it is applicable to a variety of differential coding problems which may appear in the future.

Cited by 2